This invention relates generally to the measurement of wind direction and speed, and to the omnidirectional measurement of aerodynamic drag forces, and more particularly to solid state electronic measurement devices for use in aircraft in determining real-time relative air velocity, angle-of-sideslip, and angle-of-attack.
Conventional flow sensors such as flow probes are employed to measure fluid flow. However, such conventional sensors suffer from not being able to accurately measure fluid flow which varies widely in magnitude as well as direction, e.g., reversal of fluid flow direction. In many situations, such as aircraft stall and jet engine compressor surge, changes in flow direction take place very rapidly thereby compounding the difficulty in accurately determining fluid flow. Knowledge of fluid flow magnitude and direction is especially important in developmental aerodynamics which require a reliable in-flight flow measurement device for high angle-of-attack and stall/spin research.
Reliable ground-based and/or in-flight airflow speed, i.e., magnitude, and direction detection is also important in military and civilian aviation, military and civilian marine operations and activities, military and civilian weather stations, automotive research development, military and civilian in-flight monitoring, military field applications, and home and educational activities. For example, air bases, airports, ships and harbor control can all benefit from improved fluid flow measurement methods and devices.
Conventional wind direction and speed sensors range in complexity from the traditional wind sock which flies over many civilian and military airports to much more elaborate sensors based on nuclear, laser or sonic technology. Each of these methods has certain advantages and disadvantages in terms of cost and performance. For example, the wind sock, although it can provide valuable information, is often difficult to spot by an incoming pilot. Spinning-cup/propeller anemometers and hot-wire anemometers are life-limited due to inherently fragile components. More elaborate sensors such as the laser, sonic and nuclear anemometers are prohibitively expensive for many applications.
In additional to inadequately measuring airflow speed and direction, conventional flow sensors are not cost effective for many applications. For example, conventional flow sensors do not cost effectively operate under icing conditions, or in non-clean environments such as when exposed to dirt, insects and rain. Such sensors have also been found to perform less than adequately at airflow speeds in the range of approximately Mach 0.1 to Mach 0.8, at high altitudes such as 10 kilometers, with a suitable directional accuracy such as .+-.1.degree. for in-flight angle-of-attack (AOA) and angle-of-sideslip (AOS) monitoring, and/or in low wind speed ranges such as 5-100 knots with suitable accuracies such as an airflow accuracy of .+-.2 knots and an angular directional accuracy of .+-.2.degree. in all possible directions.